Kapiti Coast's miniature railway has been closed down amid safety concerns, right in the middle of its busiest season.

WorkSafe New Zealand said this week that the Kapiti Miniature Railway at Raumati Beach would stay shut until passenger safety concerns were allayed.

But organisers for the not-for-profit attraction have called the timing of the decision cynical and said it had left members "surprised and dismayed".

WorkSafe chief investigations inspector Alan Cooper said an investigation began after a family was tipped from the train as it rounded a curve in September. Nobody was seriously injured in the accident.

"This is a community attraction, and closing it down at holiday time was not a decision we took lightly, but I could not look a parent in the eye if another incident occurred and a child was injured," he said.

The railway was closed briefly in 2008 after another accident.

Mr Cooper said that, since then, the operators had failed to properly maintain its registration.

The report raised safety concerns about the railway's narrow gauge, the "fundamental instability of the straddle carriages" and its design, which made it prone to tip at speeds or in the wind.

But Graeme Brown, a member of the Kapiti Miniature Railway & Model Engineering Society's committee, said the train carried thousands of passengers safely each year and the decision was a "gross overreaction".

The report was flawed because it was based on a full-sized railway and the society disputed some of its conclusions,

There were some findings in the report the society "vigorously disputed", including concerns about the stability of carriages, he said.

Kapiti Railway executive committee member Laurie Bason said there had only been two incidents in the 35 years the train had been running.

About 55,000 people rode the train a year.

The train also did regular charity runs and was popular with schools and kindergartens.

"We do not have problems with children but adults do not listen to what you tell them," Mr Bason said.

Passengers were always given strict instructions before hopping on board to remain seated, keeping their feet on the running boards, and not to lean out or stand up, he said.

A family had not tipped off the train, he said. Instead a woman had leaned out to the side, making her unstable, and she had fallen out, he said.

Contrary to the accident report, the rail gauge they used was standard throughout the country and overseas.